Which of the following observations confirms that a hydrocarbon is unsaturated?
AIt has a low boiling point.
BIt decolourises bromine water at room temperature.CORRECT
CIt burns with a sooty flame.
DIt is insoluble in water.
JUPEBChemistryOrganic Chemistry: Hydrocarbons
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Why the answer is B, and why the others tempt you.
Alkenes and alkynes add bromine across their double or triple bonds, turning the orange-brown bromine water colourless; alkanes do not react without light. A sooty flame suggests a high carbon content but is not conclusive, and insolubility and low boiling point are common to all small hydrocarbons.
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